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Sunlight is like a magical energy source in the plant world, playing a crucial role in every leaf and flower in our homes. Without sufficient sunlight, even the most resilient plants can become limp and unhealthy.
Light provides the energy needed for photosynthesis and directly influences factors such as growth rate, leaf color, stem hardness, and flowering.
Simply put, light is like a nutritional meal for plants – too much or too little won’t do; it needs to be just right to ensure they grow healthy and beautiful.
Speaking of just right, this brings us to the issue of light intensity.
Accurately measuring and adjusting the light intensity in the indoor planting environment is as crucial as customizing a nutrition plan for each plant. With precise data, we can better simulate the lighting conditions found in nature, allowing each plant to thrive in its optimal light environment, growing happily and blossoming beautifully.
To help indoor gardening enthusiasts better care for their houseplants, let’s discuss a few basic concepts related to light intensity simply and understandably!
Light Intensity: It’s like turning on a light in a room – how bright the light is represents the light intensity. In gardening, it measures the amount of visible light flux received per unit area, often expressed in units called lux (lx).
However, in plant growth research, we are more concerned with the portion of light that is effective for photosynthesis in plants.
Photoperiod: This is like setting a biological clock for plants. It refers to the duration of light and darkness alternation, such as 12 hours of light followed by 12 hours of darkness, which is a typical 12/12 photoperiod.
Different plants have different preferences for photoperiod lengths, which directly affects their growth stages, including flowering and dormancy.
Photosynthetic Photon Flux Density (PPFD): This measures the amount of light that is truly useful for plant growth. PPFD quantifies the number of photosynthetically active photons that reach a unit area of the plant’s surface per unit time.
Its unit is micromoles per square meter per second (μmol/m²·s). It’s crucial because only photons within specific wavelength ranges can stimulate plants to undergo photosynthesis and synthesize the nutrients they need.
Application of PPFD in plant growth: PPFD is like the “food quantity” for plants. When plant leaves receive sufficient PPFD, they can efficiently carry out photosynthesis, producing more energy and oxygen to promote growth.
Different plant species have varying PPFD requirements at different growth stages. For instance, vegetable crops often require higher PPFD to ensure yield, while some foliage plants may adapt well to lower PPFD levels.
Handheld Light Meters/Light Quantum Meters
They are like mini detectives in your hand—compact and lightweight, allowing you to directly measure light intensity near plants or under LED grow lights. Simply aim the meter at the light source, press the button, and the display screen will show the light intensity value.
The advantage of handheld meters is their flexibility and convenience, making them particularly suitable for home gardening enthusiasts and small-scale greenhouse environments.
Hanging/Fixed Light Meters/Light Quantum Meters
If you have a large indoor farm or a large plant room at home, then this type of measurement tool is more suitable for you. These types of meters can be permanently fixed in one place, continuously monitoring the lighting conditions, and recording the changes in light intensity throughout the day, allowing you to understand the distribution and stability of light in the entire space at any time.
Smart Light Measurement Devices
Smart light measurement tools typically come with wireless transmission capabilities, allowing real-time data to be sent to a smartphone app or computer. They may even have the ability to automatically adjust the brightness and switch times of LED grow lights.
These intelligent devices eliminate the hassle of manually reading and recording data, making them especially suitable for tech enthusiasts and busy urban farmers.
When selecting a light measurement tool, consider the following aspects:
Functional Requirements: If you simply want to get a rough idea of the light intensity on your windowsill at home, a basic handheld light meter will suffice. However, if you are serious about indoor gardening, especially if you use LED grow lights, you should consider purchasing a quantum light meter to precisely adjust your light formula.
Measurement Accuracy: The more precise the device, the more accurate the measurements, but also the higher the price. Decide on the level of precision you need based on your requirements for light control.
Budget Considerations: Light measurement products on the market vary in price, ranging from basic models that cost tens of dollars to professional-grade ones that cost thousands of dollars. Choose a tool that fits your budget. Remember, cost-effectiveness is key.
Convenience and Expandability: If you plan to expand your cultivation scale or add automated facilities in the future, consider investing in smart devices that support remote monitoring and linkage control.
Conducting light intensity measurements at different positions within the plant canopy is based on the fact that light attenuates as it passes through plant leaves and branches, and there are significant differences in light conditions between the interior and the edge of the canopy.
This means that the light intensity received by different parts of the plant is not uniform. To ensure that each part receives sufficient light, you need to measure at the following positions:
During measurement, place the light meter at the same plane as the leaves, mimicking the angle at which the leaves receive light, to ensure that the data accurately reflects the actual light environment of the plant.
To obtain comprehensive light data, you need to conduct multiple measurements at different times of the day because the position of the sun and the intensity of daylight change over time. For example:
After sunset: If supplementary lighting is used (such as LED grow lights), record the artificial light intensity during the night.
Each measurement should be accompanied by recording the time and corresponding light intensity value. This allows you to plot a daily variation curve of light intensity, providing a basis for subsequent adjustments.
Upon receiving the light intensity data, you can compare it with the light requirements of different plants to assess if the current lighting conditions are suitable.
Height: If the bottom leaves receive insufficient light, try lowering the light fixture height to reduce light attenuation and increase bottom light intensity.
Angle: Adjusting the light fixture angle can alter light distribution, ensuring more uniform coverage over the entire canopy.
Light duration: Based on the measurement results, adjust the light duration accordingly to meet the daily light cycle requirements of the plants.
Continuous experimentation and fine-tuning are key to finding the optimal lighting settings. By regularly checking and recording changes in light intensity, you can dynamically optimize the lighting scheme to ensure that plants are always in the most suitable lighting environment, thereby promoting healthy and rapid growth.
Green pothos
As a common indoor foliage plant, green pothos have good shade tolerance and thrive in relatively low light conditions. The ideal light intensity for green pothos is approximately 100-200 μmol/m²·s.
Even in low-light areas, green pothos can still grow, but if the light is too strong, signs of leaf burn may appear.
Herbs
Although herbs can survive in partial shade conditions, providing relatively high light intensity is recommended to ensure their aroma and growth vigor. Generally, the ideal light intensity for herbs is between 300-600 μmol/m²·s.
Annual herbs like basil grow more vigorously in adequate light conditions, while perennial herbs like mint can adapt to lower light but still require some light stimulation to maintain good growth and aroma accumulation.
Leafy vegetables
Leafy vegetables like lettuce and spinach have relatively low light requirements but still need some light to ensure photosynthesis. The ideal light intensity for leafy vegetables is typically between 200-500 μmol/m²·s.
Bean sprouts, which grow rapidly and have a very short lifecycle, have relatively lower light requirements.
Cannabis
Cannabis is a light-sensitive plant, especially during the early growth and flowering stages, where light intensity is crucial for its growth and yield. To obtain high-quality cannabis, growers typically provide high-intensity light, with the ideal light intensity ranging between 400-1000 μmol/m²·s. Particularly during the seedling and flowering stages, light intensity should not be lower than 600 μmol/m²·s.
Strawberries
Although strawberries have some shade tolerance, to achieve abundant fruits and good flavor, the ideal light intensity should be between 300-800 μmol/m²·s, especially during the flowering and fruiting stages, when higher light levels are needed.
Tomatoes
Tomatoes are typical sun-loving plants, and sufficient light intensity greatly impacts their growth, development, and yield. When grown indoors, the light intensity for tomatoes should be at least 500-1000 μmol/m²·s, particularly during the fruiting stage.
Higher light intensity during this stage aids in fruit ripening and sugar accumulation, thereby improving the quality and yield of tomatoes.
From custom light planning, to tailored quotes, and everything in between, our team of horticulture experts are always ready to assist.
We are a professional LED plant light manufacturer, committed to using technology to enhance the maximum potential of the lamp, continuously maximizing the benefits for growers, and saving energy for the planet.
